Humans could become toxic in the future

Could humans develop poison? According to a recent study that analyzed the evolutionary prospects of mammals, this may be possible, not only for humans, but for other animal species such as monkeys or mice.

People are highly unlikely to join rattlesnakes and platypuses on the list of the most poisonous animals, but researchers say humans have all the tools they need to produce poison. Like all reptiles and mammals.

The research focused on analyzing how venom has evolved over 100 times in the animal kingdom and why, regardless of non-venomous ancestors, this collection of flexible genes, which in humans are associated to the salivary glands, constitute the majority of species. potentially toxic.

“Basically we have all the basics in place”, said study co-author Agneesh Barua, a doctoral student in evolutionary genetics at the Okinawa Institute of Science and Technology in Japan. “Now it’s up to evolution to get us there.”

Oral poison is common throughout the animal kingdom, present in creatures as diverse as spiders, snakes and Loris planks, the only known poisonous species of primates. Biologists knew that oral venom glands are altered salivary glands, but new research reveals the molecular mechanics behind the change.

“It will be a real milestone on the ground”, said Bryan Fry, a biochemist and poison expert at the University of Queensland in Australia who was not involved in the research. “They did an absolutely stunning job on some extremely complex studios.

Poison is the ultimate example of nature’s flexibility. Many toxins present in the venom are common in very different animals; Some components of centipede venom, for example, are also found in snake venom, said Ronald Jenner, a venom researcher at the Natural History Museum in London who was not involved in the research.

The new study does not focus on the toxins themselves, as they evolve rapidly and are a complex mixture of compounds. Instead, Barua and study co-author Alexander Mikheyev, an evolutionary biologist at Australian National University who focuses on the “house” genes, they say the genes are associated with the venom but are not responsible for creating the toxins themselves. These regulatory genes form the basis of the entire venom system.

Researchers started with the genome of the Taiwanese habu (Trimeresurus mucrosquamatus), a well-studied brown viper, in part because it is an invasive species in Okinawa.

“Since we know the function of all the genes present in animals, we were able to see which genes the genes of the venom are associated with”, Said Barua.

The team discovered a constellation of genes common in several body tissues in all amniotes. Amniotes are animals that fertilize their eggs internally or lay eggs on the ground; they include reptiles, birds and some mammals.

Many of these genes are involved in protein folding, Barua said, which makes sense, because poisonous animals have to produce a lot of toxins, which are made up of proteins.

“A tissue like this really has to make sure that the protein it produces is of high quality ”, He said.

Not surprisingly, the same types of household regulatory genes are found in abundance in the human salivary gland, which also produces a significant stew of protein, found in saliva, in large quantities.. This genetic basis is what enables the wide range of independently evolved poisons throughout the animal kingdom.

In other words, every mammal or reptile has the genetic scaffold on which an oral venom system is built. And humans (along with mice) also produce a key protein that is used in many venom systems. Kallikreins, which are proteins that digest other proteins, are secreted in saliva; they are also a key component of many poisons.

That’s because kallikreins are very stable proteins, Fry said, and they don’t just stop working when mutated. Therefore, it is easy to obtain beneficial mutations of kallikreins that make the venom more painful and deadly (one effect of kallikreins is a sharp drop in blood pressure).

“It is no coincidence that kallikrein is the type of compound most secreted in poisons throughout the animal kingdom, because in whatever form it is a very active enzyme and it will start to make bad things. Said Fry.

Kallikreins are therefore a natural starting point for theoretically toxic humans.

If after the 2020 drama Barua joked, “People need to be toxic to survive, we may start to see increasing doses of kallikrein.”

But that’s not as likely, unless currently successful human strategies for acquiring food and choosing a mate start to crumble, anyway. The venom most often evolves as a method of defense or as a means of controlling preyJenner told Live Science. The type of poison that evolves largely depends on how the animal lives.

Evolution can essentially tailor venom to an animal’s needs through natural selection, Fry said.

Humans, of course, have invented tools, weapons, and social structures that do most of this work without the need for poisonous fangs. And poison is expensive too, Fry said. Building and folding all of these proteins requires energy. Because of this, the poison is easily lost when not in use.

There are species of sea snakes, Fry said, that have residual venom glands, but they are no longer poisonous, as they have gone from feeding on fish to feeding on fish eggs, which do not require toxic bites.

The new research may not raise much hope for new superpowers for humans, but understanding the genetics behind venom control could be the key to medicine, Fry added.

“The importance of this document goes beyond this area of ​​study, as it provides a starting platform for all of these types of interesting questions.”, he concludes.

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